Using a serial console

People have mentioned using a serial console to find out what is going on if the screen goes blank. Has anyone used one?

From what I've read you need a comms port and a serial cable, but when did you last see a computer with a comms port?

Will a USB-RS232 adapter suffice? And if so, how should it be configured?
 
with a usb-to-serial adapter, you might lose some of the messages at start, because the usb serial ports needs to be configured, and that can't happen until the kernel is loaded (and a while later). They might be buffered, but you won't know until you try.

Using a usb serial port on a FreeBSD machine (say amd64) to access the built in serial port on another FreeBSD machine (example: Raspberry Pi) works great.

Note: usb serial adapters (and usb serial ports on single board computers like the Raspberry Pi, BeagleBone, etc) comes in various models: 5V, 3.3V. Make sure you don't accidentally connect a 5V device to a device which only can handle 3.3V.

You might need to configure the serial console on the FreeBSD machine, the handbook has an example: https://docs.freebsd.org/en/books/handbook/serialcomms/#serialconsole-setup
 
Can I use a usb-to-serial adapter on a laptop if I want to see the system bootup on another system? I guess I would need another usb-to-serial adapter on the other system... unless I can find something with a RS232 port...
 
Adding to that: an on-board "COM" port was a key requirement when I was looking for a board for building my server a few years ago :) IMHO, a server shouldn't have any gfx chip, and serial console is the "natural" thing to do. A decent server board should also have a BIOS that works with a serial console.

Of course, this doesn't help when trying to get last messages from a crashing kernel… struggling with a similar issue right now, trying to debug why radeonkms.ko only loads fine every ~5th attempt on my "evergreen" hardware (PALM chip)…
 
On Intel platform that support AMT you can use Intel® AMT serial-over-LAN using Intel Manageability Commander to access the console.
Don't know anything about AMT... Is this supported on FreeBSD and how do I tell if a ThinkPad X220 supports it?
 
Is this supported on FreeBSD

Intel ME is out of band management, it's allow you to manage the computer remotely even if it's turned off or without installed OS.


Depend of the model of the CPU but according the spec it support AMT. You can check your Bios and enable it, after that you need to boot into intel ME set up the strong password.

  • Ethernet
    • Non-vPro model: Intel 82579LF Gigabit Network Connection (Lewisville), PHY, PCIe x1
    • vPro model: Intel 82579LM Gigabit Network Connection (Lewisville), PHY, PCIe x1
  • Intel Active Management Technology (iAMT)
 
Where do I find this? Is it in the BIOS?

I notice that Config -> Intel (R) AMT -> Console Type -> [ PC ANSI, VT100, VT100+, VT-UTF8]

Machine Type Model is 4290NP3
 
Only if you have vPro model: Intel 82579LM
I guess you meant the NIC....

Is this one OK?

Code:
em0@pci0:0:25:0:<------>class=0x020000 card=0x21ce17aa chip=0x15028086 rev=0x04 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = '82579LM Gigabit Network Connection (Lewisville)'
    class      = network
    subclass   = ethernet
 
Yes it's ok. You can enable Intel ME enter in the configuration usually with ctrl+P and set up the initial password and IP address then you can try to connect from another machine using intel manageability commander or mesh commander.

Note that the Intel ME password must be 8-32 symbols long with strong complexity ( at least one digit, one symbol except ":" "," ‘”’ , one lower-case letter and one upper case later" otherwise it will not allow you to set the password. The Default password is "admin" when you first initialize it from the bios.
 
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